As a gland packing which is used for preventing leakage from a rotation shaft from occurring, a string-like packing in which inorganic fibers such as asbestos fibers or glass fibers are braided by various braiding methods, and then the fibers are impregnated with a lubricant or the like or under-go surface treatment, i.e., a so-called braided packing is often used.
Many kinds of braided packings in which carbon fibers or para-aromatic polyamide fibers are used as a material have been produced. The characteristics of a gland packing, such as the heat resistance, the chemical resistance, and the abrasion resistance have been largely improved. As conventional art examples of this kind, packings disclosed in Patent Literatures 1 and 2 are known.
Among gland packings of this kind, there is a gland packing in which the number of movement paths of yarns (number of yarn paths) is 4, more specifically a grand packing which is configured by a string-like member formed by braiding a plurality of yarns, which has a rectangular section, and in which the directions of the yarns in the section are parallel to diagonal lines, and the number of the movement paths of the yarns is set to 4 (see Patent Literature 3).
In such a braided packing, usually, the string-like member is loaded to a gland portion of a pump in the following manner. The string-like member is cut to a predetermined length. Then, the string-like member is inserted in an annular shape (doughnut shape) where its ends are butted together, i.e., as a gland packing. In the insertion, in the side surface which is one of the four side surfaces of the string-like member, and which functions as the inner circumferential surface of the inserted gland packing, the yarns often tend to be flexed and bulged toward the inner center (radially inward side).
The bulge is formed as concaves and convexes on the inner circumferential surface, and adversely affects the flatness of the surface which is contacted with the stem, +with the result that there is a possibility that also the sealing performance against leakage is adversely affected.